Methods for forming a metallic film on a substrate by a cyclical deposition and related semiconductor device structures

ABSTRACT

Methods for forming a metallic film on a substrate by cyclical deposition are provided. In some embodiments methods may include contacting the substrate with a first reactant comprising a non-halogen containing metal precursor comprising at least one of copper, nickel or cobalt and contacting the substrate with a second reactant comprising a hydrocarbon substituted hydrazine. In some embodiments related semiconductor device structures may include at least a portion of a metallic interconnect formed by cyclical deposition processes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/434,051, filed on Feb. 15, 2017, and entitled “METHODS FOR FORMING AMETALLIC FILM ON A SUBSTRATE BY A CYCLICAL DEPOSITION AND RELATEDSEMICONDUCTOR DEVICE STRUCTURES,” the disclosure of which is herebyincorporated by reference in its entirety.

PARTIES OF JOINT RESEARCH AGREEMENT

The invention claimed herein was made by, or on behalf of, and/or inconnection with a join research agreement between the University ofHelsinki and ASM Microchemistry Oy. The agreement was in effect on andbefore the date the claimed invention was made, and the claimedinvention was made as a result of activities undertaken within the scopeof the agreement.

BACKGROUND Field of the Invention

The present disclosure relates generally to methods for forming ametallic film on a substrate by cyclical deposition and in particularfor forming metallic films comprising at least one of copper, cobalt andnickel. The disclosure also relates to semiconductor device structuresincluding a metallic film formed by cyclical deposition.

Description of the Related Art

Metallic films, such as metallic films comprising copper, cobalt andnickel may be utilized in the fabrication of semiconductor devicestructures. For example, copper has become the primary interconnectmaterial in microelectronic devices due to the low resistivity and highresistance to electromigration exhibited by copper films. Copperinterconnects may be fabricated by a two-step process wherein a copperseed layer is first formed by physical vapor deposition (PVD) followedby a subsequent copper fill process performed by an electrodepositionprocess. However, the development of next generation microelectronicdevices depends on the downscaling of semiconductor device featuresizes. Therefore, the copper seed layer may be required to be anextremely thin film which not only exhibits a low resistivity but whichcan also be formed in a conformal manner.

Due to the limited conformality inherent in PVD techniques, a moresuitable deposition process may be required for the conformal depositionof metallic films for utilization in the fabrication of semiconductordevice structures, such as, for example, for the formation of copperseed layers. A cyclical deposition, for example, atomic layer depositionprocesses may be utilized for forming conformal metallic films byalternating the supply of two or more gaseous precursors for reaction ata substrate surface. The reaction steps making up the atomic layerdeposition process may be self-limited which enables the deposition ofuniform and conformal metallic films with an atomic level of accuracy.

As an example, cyclical deposition of copper for fabrication ofsemiconductor device structures has been studied and may utilizeprecursors comprising copper chloride (CuCl), zinc (Zn) and hydrogen(H₂). However, the deposition of high-quality copper films at lowtemperatures has proven to be a challenging problem. Low depositiontemperatures may be utilized in cyclical deposition, such as atomiclayer deposition processes to suppress agglomeration and enable thedeposition of thin, continuous films of copper. However, the vastmajority of copper ALD processes require high temperature depositiontechniques, with lower temperature processes principally being achievedby plasma enhanced processes which may lead to deterioration of thesubstrate and poor conformal coverage.

Methods and semiconductor device structures are therefore desirable thatare able to deposit metallic films at a reduced deposition temperature,the deposition process being capable of providing a high-qualityconformal metallic films.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

In some embodiments, methods for forming a metallic film on a substrateby cyclical deposition are provided. The methods may comprise contactingthe substrate with a first reactant comprising a non-halogen containingmetal precursor comprising at least one of copper, nickel or cobalt andcontacting the substrate with a second reactant comprising a hydrocarbonsubstituted hydrazine precursor.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples ofembodiments of the disclosure when read in conjunction with theaccompanying drawings, in which:

FIG. 1 is a graph showing x-ray diffraction (XRD) scans of copper filmsformed according to the embodiments of the disclosure;

FIG. 2 is simplified cross section view of a semiconductor devicestructure formed according to the embodiments of the disclosure;

FIG. 3 illustrated a reaction system configured to perform certainembodiments of the disclosure;

FIG. 4 is a graph showing time-of-flight elastic recoil detectionanalysis (TOF-ERDA) of a copper film formed according to the embodimentsof the disclosure.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual view ofany particular material, structure, or device, but are merely idealizedrepresentations that are used to describe embodiments of the disclosure.

As used herein, the term “cyclic deposition” may refer to the sequentialintroduction of precursors (reactants) into a reaction chamber todeposit a layer over a substrate and includes processing techniques suchas atomic layer deposition and cyclical chemical vapor deposition.

As used herein, the term “atomic layer deposition” (ALD) may refer to avapor deposition process in which deposition cycles, preferably aplurality of consecutive deposition cycles, are conducted in a processchamber. Typically, during each cycle the precursor is chemisorbed to adeposition surface (e.g., a substrate surface or a previously depositedunderlying surface such as material from a previous ALD cycle), forminga monolayer or sub-monolayer that does not readily react with additionalprecursor (i.e., a self-limiting reaction). Thereafter, if necessary, areactant (e.g., another precursor or reaction gas) may subsequently beintroduced into the process chamber for use in converting thechemisorbed precursor to the desired material on the deposition surface.Typically, this reactant is capable of further reaction with theprecursor. Further, purging steps may also be utilized during each cycleto remove excess precursor from the process chamber and/or remove excessreactant and/or reaction byproducts from the process chamber afterconversion of the chemisorbed precursor. Further, the term “atomic layerdeposition,” as used herein, is also meant to include processesdesignated by related terms such as, “chemical vapor atomic layerdeposition”, “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE),gas source MBE, or organometallic MBE, and chemical beam epitaxy whenperformed with alternating pulses of precursor composition(s), reactivegas, and purge (e.g., inert carrier) gas.

As used herein, the term “cyclical chemical vapor deposition” may referto any process wherein a substrate is sequentially exposed to two ormore volatile precursors, which react and/or decompose on a substrate toproduce a desired deposition.

As used herein, the term “substrate” may refer to any underlyingmaterial or materials that may be used, or upon which a device, acircuit or a film may be formed.

As used herein, the term “hydrocarbon substituted hydrazine” may referto a derivative of hydrazine (N₂H₄) which may comprise at least onehydrocarbon substituted group.

As used herein, the term “non-halogen containing metal precursor” mayrefer to a metal precursor substantially free of halogen species.

The present disclosure includes methods for forming a metallic film on asubstrate by a cyclical deposition process and the semiconductor devicestructures themselves that include a metallic film formed by thecyclical deposition process. The methods of disclosure may includemethods for cyclical deposition of metallic films, such as, for example,copper, cobalt and nickel. The disclosure may also include utilizing themetallic film, such as copper, as at least a portion of a metallicinterconnect. The disclosure may also include methods for forming ametallic film with reduced electrical resistivity and desirablecrystallographic properties. Examples of such methods and semiconductordevices structures are disclosed in further detail below.

A non-limiting example embodiment of a cyclical deposition process mayinclude ALD, wherein ALD is based on typically self-limiting reactions,whereby sequential and alternating pulses of reactants are used todeposit about one atomic (or molecular) monolayer of material perdeposition cycle. The deposition conditions and precursors are typicallyselected to provide self-saturating reactions, such that an adsorbedlayer of one reactant leaves a surface termination that is non-reactivewith the gas phase reactants of the same reactant. The substrate issubsequently contacted with a different reactant that reacts with theprevious termination to enable continued deposition. Thus, each cycle ofalternated pulses typically leaves no more than about one monolayer ofthe desired material. However, as mentioned above, the skilled artisanwill recognize that in one or more ALD cycles more than one monolayer ofmaterial may be deposited, for example if some gas phase reactions occurdespite the alternating nature of the process.

In an ALD-type process for depositing metallic films, one depositioncycle may comprise exposing the substrate to a first reactant, removingany unreacted first reactant and reaction byproducts from the reactionspace and exposing the substrate to a second reactant, followed by asecond removal step. The first reactant may comprise a non-halogencontaining metal precursor and the second reactant may comprise ahydrocarbon substituted hydrazine precursor.

Precursors may be separated by inert gases, such as argon (Ar) ornitrogen (N₂), to prevent gas-phase reactions between reactants andenable self-saturating surface reactions. In some embodiments, however,the substrate may be moved to separately contact a first vapor phasereactant and a second vapor phase reactant. Because the reactionsself-saturate, strict temperature control of the substrates and precisedosage control of the precursors is not usually required. However, thesubstrate temperature is preferably such that an incident gas speciesdoes not condense into monolayers nor decompose on the surface. Surpluschemicals and reaction byproducts, if any, are removed from thesubstrate surface, such as by purging the reaction space or by movingthe substrate, before the substrate is contacted with the next reactivechemical. Undesired gaseous molecules can be effectively expelled from areaction space with the help of an inert purging gas. A vacuum pump maybe used to assist in the purging.

According to some embodiments, ALD processes are used to form metallicfilms on a substrate, such as an integrated circuit workpiece. In someembodiments of the disclosure each ALD cycle comprises two distinctdeposition steps or phases. In a first phase of the deposition cycle(“the metal phase”), the substrate surface on which deposition isdesired is contacted with a first vapor phase reactant comprising ametal precursor which chemisorbs onto the substrate surface, forming nomore than about one monolayer of reactant species on the surface of thesubstrate.

Reactors capable of being used to grow thin films can be used for thedeposition. Such reactors include ALD reactors, as well as CVD reactorsequipped with appropriate equipment and means for providing theprecursors. According to some embodiments, a showerhead reactor may beused.

Examples of suitable reactors that may be used include commerciallyavailable single substrate (or single wafer) deposition equipment suchas Pulsar® reactors (such as the Pulsar® 2000 and the Pulsar® 3000 andPulsar® XP ALD), and EmerALD® XP and the EmerALD® reactors, availablefrom ASM America, Inc. of Phoenix, Ariz. and ASM Europe B.V., Almere,Netherlands. Other commercially available reactors include those fromASM Japan K.K (Tokyo, Japan) under the tradename Eagle® XP and XP 8. Insome embodiments the reactor is a spatial ALD reactor, in which thesubstrates moves or rotates during processing.

In some embodiments a batch reactor may be used. Suitable batch reactorsinclude, but are not limited to, Advance® 400 Series reactorscommercially available from and ASM Europe B.V (Almere, Netherlands)under the trade names A400 and A412 PLUS. In some embodiments a verticalbatch reactor is utilized in which the boat rotates during processing,such as the A412. Thus, in some embodiments the wafers rotate duringprocessing. In other embodiments, the batch reactor comprises aminibatch reactor configured to accommodate 10 or fewer wafers, 8 orfewer wafers, 6 or fewer wafers, 4 or fewer wafers, or 2 wafers. In someembodiments in which a batch reactor is used, wafer-to-wafer uniformityis less than 3% (1 sigma), less than 2%, less than 1% or even less than0.5%.

The deposition processes described herein can optionally be carried outin a reactor or reaction space connected to a cluster tool. In a clustertool, because each reaction space is dedicated to one type of process,the temperature of the reaction space in each module can be keptconstant, which improves the throughput compared to a reactor in whichthe substrate is heated up to the process temperature before each run.Additionally, in a cluster tool it is possible to reduce the time topump the reaction space to the desired process pressure levels betweensubstrates.

A stand-alone reactor can be equipped with a load-lock. In that case, itis not necessary to cool down the reaction space between each run. Insome embodiments a deposition process for depositing a thin filmcomprising metallic film may comprise a plurality of deposition cycles,for example ALD cycles.

In some embodiments the cyclical deposition process are used to formmetallic films on a substrate and the cyclical deposition process may bean ALD type process. In some embodiments the cyclical deposition may bea hybrid ALD/CVD or cyclical CVD process. For example, in someembodiments the growth rate of the ALD process may be low compared witha CVD process. One approach to increase the growth rate may be that ofoperating at a higher substrate temperature than that typically employedin an ALD process, resulting in a chemical vapor deposition process, butstill taking advantage of the sequential introduction of precursors,such a process may be referred to as cyclical CVD.

In some embodiments, the metal precursor, also referred to herein as the“metal compound” may comprise a non-halogen containing metal precursor,i.e., the metal precursor may be substantially free of halogen species.In some embodiments, the non-halogen containing metal precursor maycomprise one of copper, cobalt and nickel. The non-halogen containingmetal precursor may therefore comprise at least one of Cu(dmap)₂(dmap=dimethylamino-2-propoxide), Ni(dmap)₂ or Co(dmap)₂. In someembodiments the non-halogen containing metal precursor may thereforecomprise at least one bidentate ligand in which the metal center atom isbonded through at least one oxygen and at least one nitrogen atom in thebidentate ligand. In some embodiments the non-halogen containing metalprecursor may therefore comprise at least one bidentate ligand in whichthe metal center atom is bonded through at least one nitrogen atom inthe bidentate ligand. In some embodiments the non-halogen containingmetal precursor may therefore comprise at least one bidentate ligand andat least one other ligand, such as monodentate ligand. In someembodiments the non-halogen containing metal precursor may thereforecomprise at least one bidentate ligand and at least two other ligands,such as monodentate ligands. In some embodiments the non-halogencontaining metal precursor may therefore comprise at least one bidentateligand and at least one other ligand, such as monodentate ligand, whichis bonded through N or O to the metal center atom. In some embodimentsthe non-halogen containing metal precursor may therefore comprise atleast one bidentate ligand in which the metal center atom is bondedthrough at least one nitrogen atom and bonded through at least one otheratom than nitrogen in the bidentate ligand. In some embodiments thenon-halogen containing metal precursor may therefore comprise at leastone bidentate ligand in which the metal center atom is bonded through attwo nitrogen atoms in the bidentate ligand. In some embodiments thenon-halogen containing metal precursor comprises at least two bidentanteligands. In some embodiments the non-halogen containing metal precursorincludes two bidentante ligands. Some examples of suitable non-halidecontaining betadiketiminato (e.g., Ni(pda)2),(pda=pentane-2,4,-diketiminato) compounds are mentioned in U.S. PatentPublication No. 2009-0197411 A1, the disclosure of which is incorporatedherein in its entirety. Some examples of suitable non-halide containingamidinate compounds (e.g., Ni(iPr-AMD)2) are mentioned in U.S. PatentPublication No. 2006-0141155 A1, the disclosure of which is incorporatedherein in its entirety. Some examples of suitable non-halide containingiminoalkoxide compounds are mentioned in U.S. Patent Publication No.2014-0227444 A1, the disclosure of which is incorporated herein in itsentirety. In some embodiments the non-halogen containing metal precursordoes not comprise other metal atoms than the desired metal (Co, Ni, Cu).In some embodiments the metal in the non-halogen containing metalprecursor has oxidation state of 0. In some embodiments the metal in thenon-halogen containing metal precursor has oxidation state of +I. Insome embodiments the metal in the non-halogen containing metal precursorhas oxidation state of +III. In some embodiments the metal in thenon-halogen containing metal precursor has oxidation state of +II. Insome embodiments the oxidation state is the oxidation state of the metalin the precursor at room temperature. The oxidation state may change indifferent conditions, such as in different pressures, temperaturesand/or atmospheres as well as when contacted with different surfacematerials at the said different conditions. In some embodiments thenon-halogen containing metal precursor does not comprise halides, suchas F, Cl, Br or I. In some embodiments the non-halogen containing metalprecursor comprises carbon, hydrogen and nitrogen and optionally oxygen.

In some embodiments the non-halide containing copper precursor maycomprise, for example, Cu(dmap)₂ or copper(I)N,N′-diisopropylacetamidinate. In some embodiments, copper precursorscan be selected from the group consisting of copper betadiketonatecompounds, copper betadiketiminato compounds, copper aminoalkoxidecompounds, such as Cu(dmae)₂, Cu(deap)₂ or Cu(dmamb)₂, copper amidinatecompounds, such as Cu(^(s)Bu-amd)]₂, copper cyclopentadienyl compounds,copper carbonyl compounds and combinations thereof. In some embodiments,X(acac)_(y) or X(thd)_(y) compounds are used, where X is copper, y isgenerally, but not necessarily 2 or 3 and thd is2,2,6,6-tetramethyl-3,5-heptanedionato. In some embodiments thenon-halide containing copper precursor is copper(II)acetate, [Cu(HMDS)]4or Cu(nhc)HMDS (1,3-di-isopropyl-imidazolin-2-ylidene copper hexamethyldisilazide) or Cu-betadiketiminates, such as Cu(dki)VTMS(dki=diketiminate).

In some embodiments the non-halide containing nickel precursor may be,for example, bis(4-N-ethylamino-3-penten-2-N-ethyliminato)nickel (II).In some embodiments, nickel precursors can be selected from the groupconsisting of nickel betadiketonate compounds, nickel betadiketiminatocompounds, nickel aminoalkoxide compounds, nickel amidinate compounds,nickel cyclopentadienyl compounds, nickel carbonyl compounds andcombinations thereof. In some embodiments, X(acac)_(y) or X(thd)_(y)compounds are used, where X is nickel, y is generally, but notnecessarily 2 or 3 and thd is 2,2,6,6-tetramethyl-3,5-heptanedionato.

In some embodiments the Co precursor is a Co beta-diketoiminatocompound. In some embodiments the Co precursor is a Co ketoiminatecompound. In some embodiments the Co precursor is a Co amidinatecompound. In some embodiments the Co precursor is a Co beta-diketonatecompound. In some embodiments the Co precursor contains at least oneketoimine ligand or a derivative thereof. In some embodiments the Coprecursor contains at least one amidine ligand or a derivative thereof.In some embodiments the Co precursor contains at least one ketonateligand or a derivative thereof. In some embodiments the Co precursor isCo₂(CO)₈, CCTBA, CoCp₂, Co(Cp-amd), Co(Cp(CO)₂), tBu-AllylCo(CO)₃ orCo(HMDS)₂.

In some embodiments, exposing the substrate to the non-halogencontaining metal precursor may comprise pulsing the metal precursor(e.g., the Cu(dmap)₂) over the substrate for a time period of betweenabout 0.01 seconds and about 60 seconds, between about 0.05 seconds andabout 10.0 seconds, between about 0.1 seconds and about 5.0 seconds. Inaddition, during the pulsing of the metal precursor over the substratethe flow rate of the metal precursor may be less than 2000 sccm, or lessthan 1000 sccm, or less than 500 sccm, or less than 200 sccm or evenless than 100 sccm.

Excess metal precursor and reaction byproducts (if any) may be removedfrom the substrate surface, e.g., by purging with an inert gas. Forexample, in some embodiments of the disclosure the methods may include apurge cycle wherein the substrate surface is purged for time period ofless than approximately 1.0 seconds. Excess metal precursor and anyreaction byproducts may be removed with the aid of a vacuum generated bya pumping system.

In a second phase of the deposition cycle (“substituted hydrazinephase”), the substrate is contacted with a second vapor phase reactantcomprising a hydrocarbon substituted hydrazine precursor. In someembodiments of the disclosure, methods may further comprise selectingthe substituted hydrazine to comprise an alkyl group with at least four(4) carbon atoms, wherein “alkyl group” refers to a saturated orunsaturated hydrocarbon chain of at least four (4) carbon atoms inlength, such as, but not limited to, butyl, pentyl, hexyl, heptyl andoctyl and isomers thereof, such as n-, iso-, sec- and tert-isomers ofthose. The alkyl group may be straight chain or branched-chain and mayembrace all structural isomer forms of the alkyl group. In someembodiments the alkyl chain might be substituted. In some embodiments ofthe disclosure, the alkyl-hydrazine may comprise at least one hydrogenbonded to nitrogen. In some embodiments of the disclosure, thealkyl-hydrazine may comprise at least two hydrogens bonded to nitrogen.In some embodiments of the disclosure, the alkyl-hydrazine may compriseat least one hydrogen bonded to nitrogen and at least one alkyl chainbonded to nitrogen. In some embodiments of the disclosure, the secondreactant may comprise an alkyl-hydrazine and may further comprise one ormore of tertbutylhydrazine (C₄H₉N₂H₃), dimethylhydrazine ordiethylhydrazine. In some embodiments of the disclosure, the substitutedhydrazine has at least one hydrocarbon group attached to nitrogen. Insome embodiments of the disclosure, the substituted hydrazine has atleast two hydrocarbon groups attached to nitrogen. In some embodimentsof the disclosure, the substituted hydrazine has at least threehydrocarbon groups attached to nitrogen. In some embodiments of thedisclosure, the substituted hydrazine has at least one C1-C3 hydrocarbongroup attached to nitrogen. In some embodiments of the disclosure, thesubstituted hydrazine has at least one C4-C10 hydrocarbon group attachedto nitrogen. In some embodiments of the disclosure, the substitutedhydrazine has linear, branched or cyclic or aromatic hydrocarbon groupattached to nitrogen. In some embodiments of the disclosure thesubstituted hydrazine comprises substituted hydrocarbon group attachedto nitrogen.

In some embodiments of the disclosure, the substituted hydrazine has thefollowing formula:R^(I)R^(II)—N—NR^(III)R^(IV),  (1)

Wherein R^(I) can be selected from hydrocarbon group, such as linear,branched, cyclic, aromatic or substituted hydrocarbon group and each ofthe R^(II), R^(III), R^(IV) groups can be independently selected to behydrogen or hydrocarbon groups, such as linear, branched, cyclic,aromatic or substituted hydrocarbon group.

In some embodiments in the formula (1) each of the R^(I), R^(II),R^(III), R^(IV) can be C1-C10 hydrocarbon, C1-C3 hydrocarbon, C4-C10hydrocarbon or hydrogen, such as linear, branched, cyclic, aromatic orsubstituted hydrocarbon group. In some embodiments at least one of theR^(I), R^(II), R^(III), R^(IV) groups comprises aromatic group such asphenyl group. In some embodiments at least one of the R^(I), R^(II),R^(III), R^(IV) groups comprises methyl, ethyl, n-propyl, propyl,n-butyl, i-butyl, s-butyl, tertbutyl group or phenyl group. In someembodiments at least two of the each R^(I), R^(II), R^(III), R^(IV)groups can be independently selected to comprise methyl, ethyl,n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, tertbutyl group or phenylgroup. In some embodiments R^(II), R^(III), R^(IV) groups are hydrogen.In some embodiments at least two one of the R^(II), R^(III), R^(IV)groups are hydrogen. In some embodiments at least one of the R^(II),R^(III), R^(IV) groups are hydrogen. In some embodiments all of theR^(II), R^(III), R^(IV) groups are hydrocarbons.

In some embodiments, exposing the substrate to the substituted hydrazineprecursor may comprise pulsing the substituted hydrazine precursor(e.g., tertbutylhydrazine) over the substrate for a time period ofbetween 0.1 seconds and 2.0 seconds or from about 0.01 seconds to about10 seconds or less than about 20 seconds, less than about 10 seconds orless than about 5 seconds. During the pulsing of the substitutedhydrazine precursor over the substrate the flow rate of the substitutedhydrazine precursor may be less than 2000 sccm, or less than 1000 sccm,or less than 500 sccm, or even less than 100 sccm.

The second vapor phase reactant comprising an substituted hydrazineprecursor may react with the metal-containing molecules left on thesubstrate surface. In some embodiments, the second phase substitutedhydrazine precursor may comprise a reducing agent capable of reducingthe metal-containing molecules left on the substrate surface to therebyform a metallic film. For example, the first vapor phase reactant maycomprise a copper precursor and the second vapor phase reactant maycomprise a reducing agent. After the copper precursor is introduced intothe reaction chamber and adsorb onto a substrate surface, the excesscopper precursor vapor may be pumped or purged from the chamber. Thisprocess is followed by the introduction of a reducing agent that reactswith the copper precursor on the substrate surface to form a coppermetal and a free form of the ligand. This deposition cycle can berepeated if needed to achieve the desired thickness of the metallicfilm.

Excess second source chemical and reaction byproducts, if any, may beremoved from the substrate surface, for example by a purging gas pulseand/or vacuum generated by a pumping system. Purging gas is preferablyany inert gas, such as, without limitation, argon (Ar), nitrogen (N₂) orhelium (He). A phase is generally considered to immediately followanother phase if a purge (i.e., purging gas pulse) or other reactantremoval step intervenes.

The deposition cycle in which the substrate is alternatively contactedwith the first vapor phase reactant (i.e., the non-halogen containingmetal precursor) and the second vapor phase reactant (i.e., thesubstituted hydrazine precursor) may be repeated two or more times untila desired thickness of a metallic film is deposited. It should beappreciated that in some embodiments of the disclosure the order of thecontacting of the substrate with the first vapor phase reactant and thesecond phase reactant may be such that the substrate is first contactedwith the second vapor phase reactant followed by the first vapor phasereactant. In addition in some embodiments the cyclical depositionprocess may comprise contacting the substrate with the first vapor phasereactant one or more times prior to contacting the substrate with thesecond vapor phase reactant one or more times and similarly mayalternatively comprise contacting the substrate with the second vaporphase reactant one or more times prior to contacting the substrate withthe first vapor phase reactant one or more times. In addition, someembodiments of the disclosure may comprise selecting the first vaporphase reactant and the second vapor phase reactant to comprisenon-plasma reactants, e.g., the first and second vapor phase reactantsare substantially free of ionized reactive species. In some embodimentsthe first and second vapor phase reactants are substantially free ofionized reactive species, excited species or radical species. Forexample, both the first vapor phase reactant and the second vapor phasereactant may comprise non-plasma reactants to prevent ionization damageof the underlying substrate and the associated defects.

The cyclical deposition processes described herein, utilizing anon-halogen containing metal precursor and a substituted hydrazineprecursor to form a metallic film, may be performed in an ALD or CVDdeposition system with a heated substrate. For example, in someembodiments, methods may comprise heating the substrate to temperatureof between approximately 80° C. and approximately 140° C., or evenheating the substrate to a temperature of between approximately 80° C.and approximately 120° C. Of course, the appropriate temperature windowfor any given cyclical deposition process, such as, for an ALD reaction,will depend upon the surface termination and reactant species involved.Here, the temperature varies depending on the precursors being used andis generally at or below about 700° C., in some embodiments thedeposition temperature is generally at or above about 100° C. for vapordeposition processes, in some embodiments the deposition temperature isbetween about 100° C. and about 250° C., and in some embodiments thedeposition temperature is between about 120° C. and about 200° C. Insome embodiments the deposition temperature is below about 500° C.,below about 400° C. or below about 300° C. In some instances thedeposition temperature can be below about 200° C., below about 150° C.or below about 100° C., for example, if additional reactants or reducingagents, such as ones reactants or reducing agents comprising hydrogen,are used in the process. In some instances the deposition temperaturecan be above about 20° C., above about 50° C. and above about 75° C.

Thin films comprising a metallic film deposited according to some of theembodiments described herein may be continuous thin films comprising ametallic film. In some embodiments the thin films comprising a metallicfilm deposited according to some of the embodiments described herein maybe continuous at a thickness below about 100 nm, below about 60 nm,below about 50 nm, below about 40 nm, below about 30 nm, below about 25nm, or below about 20 nm or below about 15 nm or below about 10 nm orbelow about 5 nm or lower. The continuity referred to herein can bephysically continuity or electrical continuity. In some embodiments thethickness at which a film may be physically continuous may not be thesame as the thickness at which a film is electrically continuous, andthe thickness at which a film may be electrically continuous may not bethe same as the thickness at which a film is physically continuous.

While in some embodiments a thin film comprising a metallic filmdeposited according to some of the embodiments described herein may becontinuous, in some embodiments it may be desirable to form anon-continuous thin film comprising a metallic film, or a thin filmcomprising separate islands or nanoparticles comprising a metallic film.In some embodiments the deposited thin film comprising a metallic filmmay comprise nanoparticles comprising copper, nickel or cobalt that arenot substantially physically or electrically continuous with oneanother. In some embodiments the deposited thin film comprising ametallic film may comprise separate nanoparticles, or separate islands,comprising a metallic film.

In some embodiments a thin film comprising a metallic film depositedaccording to some of the embodiments described herein may have anelectrical resistivity of less than about 20 μΩcm at a thickness of lessthan about 100 nm. In some embodiments a thin film comprising a metallicfilm deposited according to some of the embodiments described herein mayhave an electrical resistivity of less than about 20 μΩcm at a thicknessof below about 60 nm, below about 50 nm, below about 40 nm, below about30 nm, below about 25 nm, or below about 20 nm or lower. In someembodiments a thin film comprising a metallic film deposited accordingto some of the embodiments described herein may have an electricalresistivity of less than about 15 μΩcm at a thickness of below about 60nm, below about 50 nm, below about 40 nm, below about 30 nm, below about25 nm, or below about 20 nm or lower. In some embodiments a thin filmcomprising a metallic film deposited according to some of theembodiments described herein may have an electrical resistivity of lessthan about 10 μΩcm at a thickness of below about 60 nm, below about 50nm, below about 40 nm, below about 30 nm, below about 25 nm, or belowabout 20 nm or lower.

In some embodiments a thin film comprising metallic film depositedaccording to some of the embodiments described herein may have anelectrical resistivity of less than about 200 μΩcm at a thickness ofbelow about 30 nm, below about 20 nm, below about 15 nm, below about 10nm, below about 8 nm, or below about 5 nm or lower.

In some embodiments a metallic thin film deposited according to some ofthe embodiments described herein may have an electrical resistivity ofless than about 200 μΩm, less than about 100 μΩcm, less than about 50μΩcm, less than about 30 μΩcm, less than about 20 μΩcm, less than about18 μΩcm, less than about 15 μΩcm, less than about 12 μΩcm, less thanabout 10 μΩcm or less than about 8 μΩcm at a thickness of less thanabout 100 nm.

In some embodiments a thin film comprising copper deposited according tosome of the embodiments described herein may have an electricalresistivity of less than about 200 μΩcm, less than about 100 μΩcm, lessthan about 50 μΩcm, less than about 30 μΩcm, less than about 20 μΩcm,less than about 18 μΩcm, less than about 15 μΩcm, less than about 12μΩcm, less than about 10 μΩcm, less than about 8 μΩcm, or less thanabout 5 μΩcm or lower at a thickness of less than about 100 nm. In someembodiments a thin film comprising copper deposited according to some ofthe embodiments described herein may have an electrical resistivity ofless than about 20 μΩcm, less than about 18 μΩcm, less than about 15μΩcm, less than about 12 μΩcm, less than about 10 μΩcm, less than about8 μΩcm, or less than about 5 μΩcm or lower at a thickness of less thanabout 50 nm. In some embodiments of the disclosure, forming the metallicfilm (e.g., the copper film) may comprise forming the metallic film tohave an electrical resistivity of less than approximately 4 μΩ-cm, or anelectrical resistivity of less than 3 μΩ-cm, or even an electricalresistivity of less than 2 μΩ-cm. As a non-limiting example, a copperfilm may be formed by the methods of the disclosure to a thickness ofapproximately 50 nanometers with an electrical resistivity ofapproximately 1.92 μΩ-cm.

In some embodiments a thin film comprising nickel or cobalt depositedaccording to some of the embodiments described herein may have anelectrical resistivity of less than about 200 μΩcm, less than about 100μΩcm, less than about 50 μΩcm, less than about 30 μΩcm, less than about20 μΩcm, less than about 18 μΩcm, less than about 15 μΩcm, less thanabout 12 μΩcm, less than about 10 μΩcm or less than about 8 μΩcm, at athickness of less than about 100 nm. In some embodiments a thin filmcomprising nickel or cobalt deposited according to some of theembodiments described herein may have an electrical resistivity of lessthan about 20 μΩcm, less than about 18 μΩcm, less than about 15 μΩcm,less than about 12 μΩcm, less than about 10 μΩcm, less than about 8 μΩcmat a thickness of less than about 50 nm.

In some embodiments a thin film comprising copper, nickel or cobaltdeposited according to some of the embodiments described herein may becrystalline or polycrystalline. In some embodiments a thin filmcomprising copper, nickel or cobalt deposited according to some of theembodiments described herein may have a cubic crystal structure. In someembodiments a thin film comprising copper, nickel or cobalt depositedaccording to some of the embodiments described herein may have athickness from about 20 nm to about 100 nm. In some embodiments a thinfilm comprising copper, nickel or cobalt deposited according to some ofthe embodiments described herein may have a thickness from about 20 nmto about 60 nm. In some embodiments a thin film comprising copper,nickel or cobalt deposited according to some of the embodimentsdescribed herein may have a thickness greater than about 20, greaterthan about 30 nm, greater than about 40 nm, greater than about 50 nm,greater than about 60 nm, greater than about 100 nm, greater than about250 nm, greater than about 500 nm, or greater. In some embodiments athin film comprising copper, nickel or cobalt deposited according tosome of the embodiments described herein may have a thickness of lessthan about 50 nm, less than about 30 nm, less than about 20 nm, lessthan about 15 nm, less than about 10 nm, less than about 5 nm or in someinstances the amount of copper, nickel or cobalt corresponds tothickness of less than about 5 nm, less than about 3 nm, less than about2 nm or less than about 1 nm, for example, if a non-continuous film orseparate particles or islands comprising copper, nickel or cobalt aredesired.

In some embodiments the growth rate of the metallic film is from about0.005 Å/cycle to about 5 Å/cycle, from about 0.01 Å/cycle to about 2.0Å/cycle. In some embodiments the growth rate of the film is more thanabout 0.05 Å/cycle, more than about 0.1 Å/cycle, more than about 0.15Å/cycle, more than about 0.20 Å/cycle, more than about 0.25 Å/cycle ormore than about 0.3 Å/cycle. In some embodiments the growth rate of thefilm is less than about 2.0 Å/cycle, less than about 1.0 Å/cycle, lessthan about 0.75 Å/cycle, less than about 0.5 Å/cycle or less than about0.3 Å/cycle.

In some embodiments a thin film comprising copper, nickel or cobalt maycomprise less than about 20 at-%, less than about 10 at-%, less thanabout 7 at-%, less than about 5 at-%, less than about 3 at-%, less thanabout 2 at-%, or less than about 1 at-% of impurities, that is, elementsother than Cu, Ni or Co or the metal of desired metallic film. In someembodiments the thin film comprising copper, nickel or cobalt compriseless than about 20 at-%, less than about 10 at-%, less than about 5at-%, less than about 2 at-%, or less than about 1 at-% of hydrogen. Insome embodiments the thin film comprising copper, nickel or cobalt maycomprise less than about 10 at-%, less than about 5 at-%, less thanabout 2 at-%, less than about 1 at-% or less than about 0.5 at-% ofcarbon. In some embodiments the thin film comprising copper, nickel orcobalt may comprise less than about 5 at-%, less than about 2 at-%, lessthan about 1 at-%, less than about 0.5 at-%, or less than about 0.2 at-%of nitrogen. In some embodiments the thin film comprising copper, nickelor cobalt may comprise less than about 15 at-%, less than about 10 at-%,less than about 5 at-%, less than about 3 at-%, less than about 2 at-%,or less than about 1 at-% of oxygen. In some embodiments the thin filmcomprising copper, nickel or cobalt may comprise less than about 30at-%, less than about 20 at-%, less than about 20 at-%, less than about5 at-%, or less than about 3 at-% of oxygen on average at the surface ofthe said copper, nickel or cobalt, wherein the surface can be understoodto be thickness of less than about 20 nm from the top most surface. Insome embodiments the thin film comprising copper, nickel or cobalt maycomprise stoichiometric or non-stoichiometric copper oxide, nickel oxideor cobalt oxide near the topmost surface of the material. In someembodiments the thin film comprising copper, nickel or cobalt maycomprise more than about 80 at-%, more than about 90 at-%, more thanabout 93 at-%, more than about 95 at-%, more than about 97 at-%, or morethan about 99 at-% copper, nickel or cobalt. As a non-limiting example,FIG. 4 illustrates a graph showing time-of-flight elastic recoildetection analysis (TOF-ERDA) of a copper film formed according to theembodiments of the disclosure.

The metallic films formed by the embodiments of the disclosure maycomprise one of copper, cobalt and nickel. In some embodiments of thedisclosure the metallic film formed may consist essentially of one ofcopper, cobalt and nickel. For example, as a non-limiting exampleembodiment, the metallic films formed by the methods of the disclosuremay comprise copper having an elemental composition of copper greaterthan 95.0 atomic %, or greater than 97.0 atomic %, or greater than 98.0atomic %, or greater than 99.0 atomic %, or even greater than 99.5atomic %. In some embodiments the copper surface might be oxidized andthe values above represent the bulk film values without surfaceoxidation. In the embodiments outlined herein, the atomic concentrationof an element may be determined utilizing Rutherford backscattering(RBS) or Time-of-Flight Elastic Recoil Detection Analysis (TOF-ERDA). Incase some other methods are used, such as x-ray photoelectronspectroscopy (XPS), the atomic concentrations may vary

In some embodiments the thin films comprising copper, nickel or cobaltmay be deposited on a three-dimensional structure. In some embodimentsthe step coverage of the thin film comprising copper, nickel or cobaltmay be equal to or greater than about 50%, greater than about 80%,greater than about 90%, about 95%, about 98% or about 99% or greater instructures having aspect ratios (height/width) of more than about 2,more than about 5, more than about 10, more than about 25, more thanabout 50 or more than about 100.

In some embodiments of the disclosure the metallic films formed by themethods described herein may have desired crystallographic properties.For example, as a non-limiting example embodiment, the metallic film mayconsist essentially of copper and the copper film may comprise a cubiccrystalline structure with a predominant (111) crystallographicorientation. In more detail, FIG. 1 is a graph showing the 2 theta x-raydiffraction (XRD) scans of non-limiting example metallic copper filmsformed by ALD process of the current disclosure utilizing a non-halogencontaining metal precursor and an alkyl-hydrazine precursor at variousdeposition temperatures. For example, the XRD scan denoted by the label100 is taken from a copper film formed by ALD utilizing Cu(dmap)₂ andtertbutylhydrazine at a substrate temperature of 140° C. The XRD scandenoted by label 100 indicates that the copper film, formed by themethods of the disclosure may comprise a number of crystallographicorientations including (111) and (200) with the (111) crystallographicorientation being predominant. Therefore, in some embodiments of thedisclosure, the metallic film, formed by the ALD processes describedherein, comprises a (111) crystallographic orientation and in someembodiments the metallic film comprises a predominant (111)crystallographic orientation.

In some embodiments the deposited thin film comprising metallic film maybe subjected to a treatment process after deposition. In someembodiments this treatment process may, for example, enhance theconductivity or continuity of the deposited thin film comprising ametallic film. In some embodiments a treatment process may comprise, forexample an anneal process. In some embodiments the thin film comprisinga metallic film may be annealed in an atmosphere comprising vacuum orone or more annealing gases, for example a reducing gas such as reducinggas comprising hydrogen. In some embodiments the metallic film maycomprise nitrogen and anneal/treatment in vacuum or anneal gas, such asin reducing gas, at elevated temperatures, for example at metallic filmdeposition reaction temperature, may reduce the nitrogen or almost fullyremove the nitrogen from the metallic film. In some embodiments thetreatment with reducing gas is applied every cycle, every n^(th) cycle,wherein n can be more than 1, 2, 3, 4, 9, 19, 49 or 99 cycles or afterthe metallic film deposition as a post-treatment. The metallic filmcomprising nitrogen before the treatment may comprise nitrogen less thanabout 60 at-%, less than about 50 at-%, less than about 40 at-%, lessthan about 30 at-%, less than about 20 at-%, less than about 10 at-%, orless than about 5 at-%. In some embodiments the metallic film after thetreatment may comprise less than about 20 at-%, less than about 10 at-%,less than about 5 at-%, less than about 2 at-%, less than about 1 at-%,less than about 0.5 at-%, or less than about 0.2 at-% of nitrogen.

The metallic films formed by the cyclical deposition processes disclosedherein can be utilized in a variety of contexts, such as in theformation of semiconductor device structures.

One of skill in the art will recognize that the processes describedherein are applicable to many contexts, including fabrication oftransistors including planar devices as well as multiple gatetransistors, such as FinFETs.

As a non-limiting example, and with reference to FIG. 2, a semiconductordevice structure 200 may comprise a interconnection structure which mayinclude a substrate 202, a barrier layer 204, a dielectric layer 206, aseed layer 208 and a fill layer 210. According to the teaching of thepresent disclosure, the seed layer 208 may comprise a metallic film,such as a metallic copper film, formed by the cyclical depositionprocesses as described herein.

In more detail, the semiconductor device structure 200 may comprise asubstrate 202 wherein the substrate 202 may comprise a silicon materialincluding device circuit components (not shown) formed in the substrate202. The barrier layer 204 may comprise an etch stop layer, such as asilicon carbide, silicon nitride, silicon oxycarbide and a siliconoxynitride. The dielectric layer 206 may comprise interlayer dielectricmaterials such as silicon dioxides, silicon nitrides, polymer basedmaterials and carbon rich dielectrics.

In some embodiments of the disclosure, the semiconductor devicestructure 200 may comprise a seed layer 208 wherein the seed layerconsists essentially of copper formed by the cyclical depositionprocesses as described herein. The seed layer may be formed to athickness of less than approximately 20 nanometers, or less thanapproximately 10 nanometers, or even less than approximately 5nanometers. In addition the seed layer may be formed to have anelectrical resistivity of less than approximately 50 μΩ-cm, less thanapproximately 20 μΩ-cm, less than approximately 10 μΩ-cm, less thanapproximately 5 μΩ-cm, less than approximately 4μΩ-cm, or an electricalresistivity of less than 3μΩ-cm, or even an electrical resistivity ofless than 2μΩ-cm.

Embodiments of the disclosure may also include a reaction systemconfigured for forming the metallic films of the present disclosure. Inmore detail, FIG. 3 schematically illustrates a reaction system 300including a reaction chamber 302 that further includes mechanism forretaining a substrate (not shown) under predetermined pressure,temperature, and ambient conditions, and for selectively exposing thesubstrate to various gases. A precursor reactant source 304 may becoupled by conduits or other appropriate means 304A to the reactionchamber 302, and may further couple to a manifold, valve control system,mass flow control system, or mechanism to control a gaseous precursororiginating from the precursor reactant source 304. A precursor (notshown) supplied by the precursor reactant source 304, the reactant (notshown), may be liquid or solid under room temperature and standardatmospheric pressure conditions. Such a precursor may be vaporizedwithin a reactant source vacuum vessel, which may be maintained at orabove a vaporizing temperature within a precursor source chamber. Insuch embodiments, the vaporized precursor may be transported with acarrier gas (e.g., an inactive or inert gas) and then fed into thereaction chamber 302 through conduit 304A. In other embodiments, theprecursor may be a vapor under standard conditions. In such embodiments,the precursor does not need to be vaporized and may not require acarrier gas. For example, in one embodiment the precursor may be storedin a gas cylinder. The reaction system 300 may also include additionalprecursor reactant sources, such precursor reactant source 306 which mayalso be couple to the reaction chamber by conduits 306A as describedabove.

A purge gas source 308 may also be coupled to the reaction chamber 302via conduits 308A, and selectively supplies various inert or noble gasesto the reaction chamber 302 to assist with the removal of precursor gasor waste gasses from the reaction chamber. The various inert or noblegasses that may be supplied may originate from a solid, liquid or storedgaseous form.

The reaction system 300 of FIG. 3, may also comprise a system operationand control mechanism 310 that provides electronic circuitry andmechanical components to selectively operate valves, manifolds, pumpsand other equipment included in the reaction system 300. Such circuitryand components operate to introduce precursors, purge gasses from therespective precursor sources 304, 306 and purge gas source 308. Thesystem operation and control mechanism 310 also controls timing of gaspulse sequences, temperature of the substrate and reaction chamber, andpressure of the reaction chamber and various other operations necessaryto provide proper operation of the reaction system 300. The operationand control mechanism 310 can include control software and electricallyor pneumatically controlled valves to control flow of precursors,reactants and purge gasses into and out of the reaction chamber 302. Thecontrol system can include modules such as a software or hardwarecomponent, e.g., a FPGA or ASIC, which performs certain tasks. A modulecan advantageously be configured to reside on the addressable storagemedium of the control system and be configured to execute one or moreprocesses.

Those of skill in the relevant arts appreciate that other configurationsof the present reaction system are possible, including different numberand kind of precursor reactant sources and purge gas sources. Further,such persons will also appreciate that there are many arrangements ofvalves, conduits, precursor sources, purge gas sources that may be usedto accomplish the goal of selectively feeding gasses into reactionchamber 302. Further, as a schematic representation of a reactionsystem, many components have been omitted for simplicity ofillustration, and such components may include, for example, variousvalves, manifolds, purifiers, heaters, containers, vents, and/orbypasses.

The example embodiments of the disclosure described above do not limitthe scope of the invention, since these embodiments are merely examplesof the embodiments of the invention, which is defined by the appendedclaims and their legal equivalents. Any equivalent embodiments areintended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternative useful combination of the elementsdescribed, may become apparent to those skilled in the art from thedescription. Such modifications and embodiments are also intended tofall within the scope of the appended claims.

What is claimed is:
 1. A method for forming a metallic film on asubstrate by cyclical deposition, the method comprising: contacting thesubstrate with a first reactant comprising a non-halogen containingmetal precursor comprising at least one bidentate ligand and at leastone of copper, nickel or cobalt to form metal-containing molecules on asurface of the substrate, wherein the non-halogen containing metalprecursor comprises at least one ligand bonded to a metal atom throughat least one oxygen atom; and contacting the substrate with a secondreactant comprising a hydrocarbon substituted hydrazine precursorcomprising a branch-chained allyl group or sec- or tert-isomer of alkylgroup of at least four carbon atoms, wherein the step of contacting thesubstrate with a second reactant immediately follows the step ofcontacting the substrate with a first reactant or immediately follows anintervening purge following the step of contacting the substrate withthe first reactant.
 2. The method of claim 1, wherein the cyclicaldeposition comprises atomic layer deposition.
 3. The method of claim 1,wherein the cyclical deposition comprises cyclical chemical vapordeposition.
 4. The method of claim 1, further comprising selecting thesubstituted hydrocarbon hydrazine precursor to comprise a C4-C8hydrocarbon group.
 5. The method of claim 1, further comprisingselecting the substituted hydrocarbon hydrazine precursor to comprise anaromatic hydrocarbon group.
 6. The method of claim 1, further comprisingselecting the substituted hydrocarbon hydrazine precursor to comprise atertbutyl alkyl group.
 7. The method of claim 6, further comprisingselecting the alkyl group to comprise at least one of a methyl, an ethylor a tertbutyl alkyl group.
 8. The method of claim 1, wherein thenon-halogen containing metal precursor comprises at least one additionalligand which is bonded to the metal atom through at least one nitrogenatom.
 9. The method of claim 1, further comprising selecting thenon-halogen containing metal precursor to comprise at least twonon-halogen containing ligands.
 10. A method for forming a metallic filmon a substrate by cyclical deposition, the method comprising: contactingthe substrate with a first reactant comprising a non-halogen containingmetal precursor comprising at least one bidentate ligand and at leastone of copper, nickel or cobalt to form metal-containing molecules on asurface of the substrate, wherein the at least one bidentate ligand isbonded through at least one nitrogen atom and bonded through at leastone atom other than nitrogen in the bidentate ligand; and contacting thesubstrate with a second reactant comprising a hydrocarbon substitutedhydrazine precursor comprising a branch-chained allyl group or sec- ortert-isomer of alkyl group of at least four carbon atoms, wherein thestep of contacting the substrate with a second reactant immediatelyfollows the step of contacting the substrate with a first reactant orimmediately follows an intervening purge following the step ofcontacting the substrate with the first reactant.
 11. The method ofclaim 10, wherein the cyclical deposition comprises atomic layerdeposition.
 12. The method of claim 10, wherein the cyclical depositioncomprises cyclical chemical vapor deposition.
 13. The method of claim10, further comprising selecting the substituted hydrocarbon hydrazineprecursor to comprise a C4-C8 hydrocarbon group.
 14. The method of claim10, further comprising selecting the substituted hydrocarbon hydrazineprecursor to comprise an aromatic hydrocarbon group.
 15. The method ofclaim 10, further comprising selecting the substituted hydrocarbonhydrazine precursor to comprise a tertbutyl alkyl group.
 16. The methodof claim 15, further comprising selecting the alkyl group to comprise atleast one of a methyl, an ethyl or a tertbutyl alkyl group.
 17. Themethod of claim 10, wherein the non-halogen containing metal precursorcomprises at least one additional ligand which is bonded to the metalatom through at least one nitrogen atom.
 18. The method of claim 10,further comprising selecting the non-halogen containing metal precursorto comprise at least two non-halogen containing ligands.
 19. A reactionsystem configured to perform the method of claim
 1. 20. A semiconductordevice structure comprising at least a portion of a metallicinterconnect formed by the method of claim 1.